It is known among builders and carpenters that the hardest part of installing a door is drilling the holes for the door knob and lock.
Some door knob and lock assemblies come with paper or cardboard templates for drilling the holes in the proper places but they tear easily. As a result a few inventors have patented complex devices to solve this problem.
U.S. Pat. No. 5,222,845 to Goldstein & Collier filed Jun. 22, 1992 describes a drill guide apparatus held in place by a clamping screw and plate and having a plurality of apertures and drill bushings.
U.S. Pat. No. 4,715,125 to Livick filed Dec. 8, 1986 comprises a pair of spaced, parallel, rectangular, frame members for clamping to a door which members have a series of pin holes for adjusting the location of tubular hole cutting guides.